CN107294603B - Visible light bilayer is superimposed Transmission system and method - Google Patents
Visible light bilayer is superimposed Transmission system and method Download PDFInfo
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Abstract
The embodiment of the invention discloses a kind of visible light bilayer superposition Transmission system and methods, the system comprises transmitting terminal and receiving ends, transmitting terminal includes coding module and LED array, and receiving end includes decoder module and camera, and information to be sent is divided into two layers of mapping transmitted by coding module；Data after mapping are modulated by OOK, modulation obtains transmission signal；Transmission signal is subjected to linear superposition and obtains superposed signal；LED array is driven after superposed signal is added direct current biasing；Decoder module is handled the LED array image that camera is shot to obtain nonnegativity signal；Nonnegativity signal is subjected to DC operation, obtain bipolar signal and carries out detection decoding, reduction obtains information to be sent.The embodiment of the present invention is transmitted by the way that the information of two kinds of different attributes is divided into two layers, solves the problems, such as to be difficult to meet Uniform Illumination when realizing higher transmission rates, and then reached and be not only able to satisfy Uniform Illumination, but also the technical effect that channel relevancy can be overcome to influence.
Description
Technical Field
The invention relates to the field of visible light imaging communication, in particular to a visible light double-layer superposition transmission system and a visible light double-layer superposition transmission method.
Background
Visible light communication has received wide attention from many researchers at home and abroad once coming out by virtue of the advantages of high broadband speed, wide coverage, no electromagnetic interference and the like. With continuous and deep research, it is found that narrow and non-linear modulation bandwidths of LEDs (light emitting diodes) are major factors restricting the rapid development of visible light communication. As is known, a Multiple Input Multiple Output (MIMO) system can improve the performance of the system by Multiple times without increasing the system bandwidth and the transmission power, and the Multiple lamp characteristics of indoor lighting and the advantages of Multiple LED lamp beads in the lamp naturally create favorable conditions for the development of the visible light MIMO technology. In addition, driven by the rapid development of modern manufacturing industry, the use of smart phones in daily life tends to be increasingly popularized and versatile. By means of a visible light imaging MIMO communication system formed by the existing LED lighting system and the smart phone, data information can be effectively transmitted on the basis of not increasing extra hardware overhead, and therefore great convenience is brought to life, traveling and the like of people. However, since the visible light communication employs the intensity modulation/direct detection technology, even if a camera is used as a receiving end for image reception, a certain channel correlation inevitably exists in the visible light MIMO channel.
In order to overcome the influence caused by channel correlation, the MIMO technology generally used includes SM technology and RC technology. The RC technology is a transmission technology with low effectiveness and high reliability, and can better meet the lighting requirement; the SM technology can achieve a high transmission rate, but it is difficult to meet the requirement of uniformity of the lighting lamp because it only uses a limited number of LED beads per transmission time slot.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a visible light double-layer overlapping transmission system and method, so as to not only satisfy uniform illumination, but also overcome the influence of channel correlation.
In order to solve the technical problem, an embodiment of the present invention provides a visible light double-layer overlapping transmission system, including a sending end and a receiving end, where the sending end includes an encoding module and an LED array for sending visible light signals, and the receiving end includes a decoding module and a camera for receiving visible light signals;
the encoding module divides information to be sent containing two types of data with different attributes into two layers for transmission mapping, wherein low-rate transmission data are distributed to an upper layer and subjected to RC mapping to complete the mapping of upper-layer transmission, high-rate transmission data are distributed to a lower layer and subjected to SM mapping to complete the mapping of lower-layer transmission, the mapped upper-layer and lower-layer data are modulated through OOK to obtain upper-layer and lower-layer transmission signals, the modulation amplitudes of the upper-layer and lower-layer data are +/- α and +/- β respectively, and the mapping relation is as follows:linearly superposing the transmission signals of the upper layer and the lower layer to obtain superposed signals; adding direct current bias to the superposed signals and driving the LED array to send corresponding visible light signals;
the decoding module processes the LED array image shot by the camera to obtain a non-negative signal; carrying out direct current removing operation on the non-negative signal, and reducing to obtain a bipolar signal; and detecting and decoding through an ML (maximum likelihood) decoding rule, and restoring to obtain information to be sent, which comprises two different attribute data.
Correspondingly, an embodiment of the present invention further provides a visible light double-layer overlapping transmission method, which is applied to the visible light double-layer overlapping transmission system, and includes:
step 1: dividing information to be sent containing two types of different attribute data into two layers for transmission mapping, wherein low-rate transmission data are distributed to an upper layer and subjected to RC mapping to finish the mapping of upper layer transmission, and high-rate transmission data are distributed to a lower layer and subjected to SM mapping to finish the mapping of lower layer transmission;
step 2: modulating the mapped upper layer and lower layer data through OOK to obtain transmission signals of the upper layer and the lower layer, and transmitting the transmission signals to the upper layer and the lower layerThe modulation amplitudes of the layer and lower layer data are + - α and + - β, respectively, and the mapping relationship is:
and step 3: linearly superposing the transmission signals of the upper layer and the lower layer to obtain superposed signals; adding direct current bias to the superposed signals and driving the LED array to send corresponding visible light signals;
and 4, step 4: processing an LED array image shot by a camera to obtain a non-negative signal; carrying out direct current removing operation on the non-negative signal, and reducing to obtain a bipolar signal; and detecting and decoding through an ML (maximum likelihood) decoding rule, and restoring to obtain information to be sent, which comprises two different attribute data.
The embodiment of the invention provides a visible light double-layer superposition transmission system and a method, wherein the system comprises a coding module, an LED array, a decoding module and a camera, and two kinds of information with different attributes are divided into two layers for transmission by adopting a two-time slot joint transmission mechanism, so that the problem that uniform illumination is difficult to meet when a higher transmission rate is realized is solved, and the technical effects of meeting the uniform illumination and overcoming the influence of channel correlation are further achieved.
Drawings
Fig. 1 is a schematic structural diagram of a visible light double-layer overlapping transmission system according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a data processing process of the visible light double-layer superposition transmission system according to the embodiment of the present invention.
Fig. 3 is a schematic diagram of a transmission frame structure according to an embodiment of the present invention.
Fig. 4 is a schematic flow chart of a visible light double-layer superposition transmission method according to an embodiment of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict, and the present invention is further described in detail with reference to the drawings and specific embodiments.
If directional indications (such as up, down, left, right, front, and rear … …) are provided in the embodiment of the present invention, the directional indications are only used to explain the relative position relationship between the components, the movement, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are only used for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.
Referring to fig. 1, the visible light double-layer overlapping transmission system of the embodiment of the invention includes a sending end and a receiving end, the sending end includes a coding module and an LED array for sending visible light signals, and the receiving end includes a decoding module and a camera for receiving visible light signals.
Referring to fig. 2, an encoding module divides information to be transmitted, which includes two different attribute data, into two layers for transmission mapping, where low-rate transmission data is allocated to an upper layer and RC (Repetition Code) mapping is performed to complete mapping of upper layer transmission, high-rate transmission data is allocated to a lower layer and SM (Spatial Modulation) mapping is performed to complete mapping of lower layer transmission, the mapped upper and lower layer data are modulated by OOK (On-Off Keying) to obtain transmission signals of the upper and lower layers, Modulation amplitudes of the upper and lower layer data are ± α and ± β, and a mapping relationship is:the upper layer and the lower layerCarrying out linear superposition on the transmission signals to obtain superposed signals; and adding the direct current offset to the superposed signal, and driving the LED array to send a corresponding visible light signal. The embodiment of the invention divides the data into two layers to transmit the data with two attributes, wherein the upper layer adopts RC technology, and the lower layer adopts SM technology, thus being capable of overcoming the influence of channel correlation; in addition, the embodiment of the invention adopts a multilayer coding superposition technology to meet the communication requirements of different distances, and simultaneously realizes the transmission of multi-attribute information data by a plurality of LED lamp beads in a single lamp.
As one embodiment, the LED array includes NtEach LED lamp bead, NtMxn; the encoding module performs SM mapping from NtP lamp beads are selected from the LED lamp beads to transmit data, so thatThe number of information bits that can be transmitted for spatial information using the SM technique is selected because the information transmission must satisfy the power of 2 relationshipAccording to the embodiment of the invention, the multiple lamp beads in a single lamp are used for communication, so that the dual requirements of illumination and communication can be met.
As an implementation manner, as shown in fig. 3, the coding module linearly superimposes each bit of transmission data by using a two-slot joint transmission mechanism, and obtains superimposed signals of the kth slot and the (k + 1) th slot by using the following formulas:
S[k]＝A[k]+B[k]；S[k+1]＝A[k+1]+B[k+1]；
respectively calculating and obtaining driving signals of the k time slot and the k +1 time slot after the direct current offset is added by adopting the following formula:
S′[k]＝S[k]+c；S′[k+1]＝S[k+1]+c；
wherein, A [ k ]]For the transmission signal of the upper layer modulated for the k-th transmission time slot, ak]∈RM×N；B[k]For the kth transmission time slot modulationThe transmission signal of the lower layer after the modulation, Bk]∈RM×N(ii) a The k +1 th transmission time slot, the transmission signal of the upper layer is the inversion signal of the k time slot, i.e. A [ k +1]]＝-A[k]The lower layer transmission signal is the same signal as k time slot, i.e. B [ k +1]]＝B[k](ii) a c is a direct current component. The embodiment of the invention adopts a two-time slot joint transmission mechanism, which not only facilitates the detection of the sending information source by the receiving end, but also facilitates the separation of double-layer superposed signals by the receiving end; in addition, the embodiment of the present invention may further obtain an information transmission rate of each attribute data:
whereinAndrespectively representing the data transmission rates of the upper and lower layers.
Referring to fig. 2, the decoding module processes the LED array image captured by the camera to obtain a non-negative signal; carrying out direct current removing operation on the non-negative signal, and reducing to obtain a bipolar signal; and detecting and decoding through an ML (Maximum Likelihood) decoding rule, and restoring to obtain information to be sent containing two different attribute data. The embodiment of the invention completes the decoding of the double-layer signal by adopting the ML decoding rule, so that the decoding complexity of the invention is lower and the optimal decoding performance is achieved.
The superposed signals are detected and received by the camera after being attenuated by the wireless optical link, the signals sent by the LED lamp beads can be detected and received by one or more pixel points on the camera, the received signals can be converted into a matrix with the same scale and size as the LED array after image processing, and the nonnegative signals after the image processing are subjected to direct current removing operation and are reduced into bipolar signals. As an implementation manner, the decoding module calculates and obtains the bipolar signals y [ k ] and y [ k +1] received in the k time slot and the k +1 time slot respectively by using the following expressions:
y[k]＝H·s[k]+n；y[k+1]＝H·s[k+1]+n；
wherein,h is a channel matrix obtained by the training sequence,s[k]and s [ k +1]]For transmitting non-negative signal column vectors, they are formed by a signal matrix S [ k ]]And S [ k +1]]Obtaining the vector through vectorization operation; n is the mean 0 and the variance isWhite gaussian noise of (1);
and calculating to obtain the optimal decision of the received data of each layer under the ML decoding criterion by adopting the following expression:
wherein | | | purple hairFExpressing the F-norm, and simplifying the above formula to obtain an equivalent expression as follows:
and respectively calculating the received judgment of each layer of data by adopting the following expression:
where a is the decision of the received upper layer low rate transmission data (i.e. the binary bit data of the low rate transmission data of the information to be transmitted)B) is the decision of the received lower layer high rate transmission data (i.e. the estimate of the binary bit data of the high rate transmission data of the information to be transmitted);represents NtA full 1 column vector of x 1; tr () represents the trace of the matrix,is a constellation set of the transmission signal of the upper layer,is the constellation set of the transmission signal of the lower layer.
As an embodiment, when the camera imaging distance is within a preset range and the quality of the imaged LED array image reaches a preset threshold (for example, when the receiving end imaging distance is suitable and the imaging effect is good), the decision expressions of the received layer data are respectively simplified into the following formulas to be calculated:
the design scheme adopted by the embodiment of the invention has the advantages of simple structure, lower decoding complexity and better decoding performance, can be applied to the existing LED green lighting resources and smart phone terminals, and can be better applied to various scenes such as street lamps, advertising screens, markets and the like, thereby providing great convenience for the life of people.
Referring to fig. 4, a visible light double-layer overlapping transmission method according to an embodiment of the present invention is applied to the visible light double-layer overlapping transmission system, and includes:
step 1: dividing information to be sent containing two types of different attribute data into two layers for transmission mapping, wherein low-rate transmission data are distributed to an upper layer and subjected to RC mapping to finish the mapping of upper layer transmission, and high-rate transmission data are distributed to a lower layer and subjected to SM mapping to finish the mapping of lower layer transmission;
step 2, modulating the mapped upper layer data and the mapped lower layer data through OOK to obtain transmission signals of the upper layer and the lower layer, wherein the modulation amplitude of the upper layer data and the modulation amplitude of the lower layer data are respectively +/- α and +/- β, and the mapping relation is as follows:
and step 3: linearly superposing the transmission signals of the upper layer and the lower layer to obtain superposed signals; adding direct current bias to the superposed signals and driving the LED array to send corresponding visible light signals;
and 4, step 4: processing an LED array image shot by a camera to obtain a non-negative signal; carrying out direct current removing operation on the non-negative signal, and reducing to obtain a bipolar signal; and detecting and decoding through an ML (maximum likelihood) decoding rule, and restoring to obtain information to be sent, which comprises two different attribute data.
As an embodiment, in the SM mapping performed in step 1, N is selected fromtSelecting p lamp beads from each LED lamp bead to transmit data, wherein N istNumber of LED beads for LED array, Nt＝M×N。
As an embodiment, in step 3:
linearly superposing each bit of transmission data by adopting a two-time slot joint transmission mechanism, and respectively calculating superposed signals of a kth time slot and a (k + 1) th time slot by adopting the following formula:
S[k]＝A[k]+B[k]；S[k+1]＝A[k+1]+B[k+1]；
respectively calculating and obtaining driving signals of the k time slot and the k +1 time slot after the direct current offset is added by adopting the following formula:
S′[k]＝S[k]+c；S′[k+1]＝S[k+1]+c；
wherein, A [ k ]]For the transmission signal of the upper layer modulated for the k-th transmission time slot, ak]∈RM×N；B[k]For the transmission signal of the lower layer after modulation of the k-th transmission time slot, B k]∈RM×N(ii) a The k +1 th transmission time slot, the transmission signal of the upper layer is the inversion signal of the k time slot, i.e. A [ k +1]]＝-A[k]The lower layer transmission signal is the same signal as k time slot, i.e. B [ k +1]]＝B[k](ii) a c is a direct current component.
As an embodiment, in step 4: the bipolar signals y [ k ] and y [ k +1] received in the k time slot and the k +1 time slot are respectively calculated by adopting the following expressions:
y[k]＝H·s[k]+n；y[k+1]＝H·s[k+1]+n；
wherein,h is a channel matrix obtained by the training sequence,s[k]and s [ k +1]]For transmitting non-negative signal column vectors, they are formed by a signal matrix S [ k ]]And S [ k +1]]Obtaining the vector through vectorization operation; n is the mean 0 and the variance isWhite gaussian noise of (1);
and calculating to obtain the optimal decision of the received data of each layer under the ML decoding criterion by adopting the following expression:
wherein | | | purple hairFExpressing the F-norm, and simplifying the above formula to obtain an equivalent expression as follows:
and respectively calculating the received judgment of each layer of data by adopting the following expression:
where a is the decision of the received upper layer low rate transmission data,ba decision for receiving lower layer high rate transmission data;represents NtA full 1 column vector of x 1; tr () represents the trace of the matrix,is a constellation set of the transmission signal of the upper layer,is the constellation set of the transmission signal of the lower layer.
As an embodiment, when the imaging distance of the camera is within a preset range and the quality of the imaged LED array image reaches a preset threshold, the decision expressions of the received data of each layer are respectively simplified into the following formulas to be calculated:
although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A visible light double-layer superposition transmission system is characterized by comprising a sending end and a receiving end, wherein the sending end comprises an encoding module and an LED array for sending visible light signals, and the receiving end comprises a decoding module and a camera for receiving the visible light signals;
the coding module divides information to be sent containing two different attribute data into two layers for transmission mapping, wherein low-rate transmission data are distributed to an upper layer and subjected to RC mapping to finish the mapping of upper layer transmission, high-rate transmission data are distributed to a lower layer and subjected to SM mapping to finish the mapping of lower layer transmissionModulating the mapped upper layer and lower layer data through OOK to obtain upper layer and lower layer transmission signals, wherein the modulation amplitude of the upper layer and lower layer data is +/- α and +/- β respectively, and the mapping relation is as follows:linearly superposing the transmission signals of the upper layer and the lower layer to obtain superposed signals; adding direct current bias to the superposed signals and driving the LED array to send corresponding visible light signals;
the decoding module processes the LED array image shot by the camera to obtain a non-negative signal; carrying out direct current removing operation on the non-negative signal, and reducing to obtain a bipolar signal; and detecting and decoding through an ML (maximum likelihood) decoding rule, and restoring to obtain information to be sent, which comprises two different attribute data.
2. The visible light dual-layer superimposed transmission system of claim 1, wherein the LED array comprises NtEach LED lamp bead, NtMxn; the encoding module performs SM mapping from NtAnd selecting p lamp beads from the LED lamp beads to transmit data.
3. The visible light double-layer superposition transmission system according to claim 2, wherein the coding module linearly superposes each bit of transmission data by using a two-slot joint transmission mechanism, and superposed signals of a k-th slot and a k + 1-th slot are respectively calculated by using the following formulas:
S[k]＝A[k]+B[k]；S[k+1]＝A[k+1]+B[k+1]；
respectively calculating and obtaining driving signals of the k time slot and the k +1 time slot after the direct current offset is added by adopting the following formula:
S′[k]＝S[k]+c；S′[k+1]＝S[k+1]+c；
wherein, A [ k ]]For the transmission signal of the upper layer modulated for the k-th transmission time slot, ak]∈RM×N；B[k]For the transmission signal of the lower layer after modulation of the k-th transmission time slot, B k]∈RM×N(ii) a The k +1 th transmission time slot, the upper layer transmission signal is the inverse signal of the k time slotNo. A [ k +1]]＝-A[k]The lower layer transmission signal is the same signal as k time slot, i.e. B [ k +1]]＝B[k](ii) a c is a direct current component.
4. The visible light double-layer superposition transmission system according to claim 3, wherein the decoding module calculates the bipolar signals y [ k ] and y [ k +1] received in the k time slot and the k +1 time slot respectively by using the following expressions:
y[k]＝H·s[k]+n；y[k+1]＝H·s[k+1]+n；
wherein,h is a channel matrix obtained by the training sequence,s[k]and s [ k +1]]For transmitting non-negative signal column vectors, they are formed by a signal matrix S [ k ]]And S [ k +1]]Obtaining the vector through vectorization operation; n is the mean 0 and the variance isWhite gaussian noise of (1);
and calculating to obtain the optimal decision of the received data of each layer under the ML decoding criterion by adopting the following expression:
wherein | | | purple hairFExpressing the F-norm, and simplifying the above formula to obtain an equivalent expression as follows:
and respectively calculating the received judgment of each layer of data by adopting the following expression:
wherein a is the judgment of the received upper layer low-rate transmission data, and b is the judgment of the received lower layer high-rate transmission data;represents NtA full 1 column vector of x 1; tr () represents the trace of the matrix,is a constellation set of the transmission signal of the upper layer,is the constellation set of the transmission signal of the lower layer.
5. The visible light double-layer superposition transmission system according to claim 4, wherein when the imaging distance of the camera is within a preset range and the quality of the imaged LED array image reaches a preset threshold, the judgment expressions of the received data of each layer are respectively simplified into the following formulas for calculation:
6. a visible light double-layer superposition transmission method applied to the visible light double-layer superposition transmission system according to any one of claims 1 to 5, comprising:
step 1: dividing information to be sent containing two types of different attribute data into two layers for transmission mapping, wherein low-rate transmission data are distributed to an upper layer and subjected to RC mapping to finish the mapping of upper layer transmission, and high-rate transmission data are distributed to a lower layer and subjected to SM mapping to finish the mapping of lower layer transmission;
step 2: modulating the mapped upper layer and lower layer data through OOK to obtain upper layer and lower layer transmission signals,the modulation amplitudes of the upper layer data and the lower layer data are respectively +/- α and +/- β, and the mapping relation is as follows:
and step 3: linearly superposing the transmission signals of the upper layer and the lower layer to obtain superposed signals; adding direct current bias to the superposed signals and driving the LED array to send corresponding visible light signals;
and 4, step 4: processing an LED array image shot by a camera to obtain a non-negative signal; carrying out direct current removing operation on the non-negative signal, and reducing to obtain a bipolar signal; and detecting and decoding through an ML (maximum likelihood) decoding rule, and restoring to obtain information to be sent, which comprises two different attribute data.
7. The visible light double-layer superposition transmission method according to claim 6, wherein in the SM mapping performed in step 1, the SM mapping is performed from NtSelecting p lamp beads from each LED lamp bead to transmit data, wherein N istNumber of LED beads for LED array, Nt＝M×N。
8. The visible light double-layer superposition transmission method according to claim 7, wherein in step 3:
linearly superposing each bit of transmission data by adopting a two-time slot joint transmission mechanism, and respectively calculating superposed signals of a kth time slot and a (k + 1) th time slot by adopting the following formula:
S[k]＝A[k]+B[k]；S[k+1]＝A[k+1]+B[k+1]；
respectively calculating and obtaining driving signals of the k time slot and the k +1 time slot after the direct current offset is added by adopting the following formula:
S′[k]＝S[k]+c；S′[k+1]＝S[k+1]+c；
wherein, A [ k ]]For the transmission signal of the upper layer modulated for the k-th transmission time slot, ak]∈RM×N；B[k]For the transmission signal of the lower layer after modulation of the k-th transmission time slot, B k]∈RM×N(ii) a The k +1 th transmission time slot, the transmission signal of the upper layer is the inversion signal of the k time slot, i.e. A [ k +1]]＝-A[k]Lower layer ofTransmitting signals in the same k time slots, i.e. B k +1]＝B[k](ii) a c is a direct current component.
9. The visible light double-layer superposition transmission method according to claim 8, wherein in step 4: the bipolar signals y [ k ] and y [ k +1] received in the k time slot and the k +1 time slot are respectively calculated by adopting the following expressions:
y[k]＝H·s[k]+n；y[k+1]＝H·s[k+1]+n；
wherein,h is a channel matrix obtained by the training sequence,s[k]and s [ k +1]]For transmitting non-negative signal column vectors, they are formed by a signal matrix S [ k ]]And S [ k +1]]Obtaining the vector through vectorization operation; n is the mean 0 and the variance isWhite gaussian noise of (1);
and calculating to obtain the optimal decision of the received data of each layer under the ML decoding criterion by adopting the following expression:
wherein | | | purple hairFExpressing the F-norm, and simplifying the above formula to obtain an equivalent expression as follows:
and respectively calculating the received judgment of each layer of data by adopting the following expression:
wherein a is the judgment of the received upper layer low-rate transmission data, and b is the judgment of the received lower layer high-rate transmission data;represents NtA full 1 column vector of x 1; tr () represents the trace of the matrix,is a constellation set of the transmission signal of the upper layer,is the constellation set of the transmission signal of the lower layer.
10. The visible light double-layer superposition transmission method according to claim 9, wherein in step 4:
when the imaging distance of the camera is within a preset range and the quality of the imaged LED array image reaches a preset threshold value, simplifying the received judgment expressions of each layer of data into the following formulas respectively for calculation:
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